Aortic dissection is a condition that affects the aorta, which is the largest artery in the body. This condition is caused by the separating/dissection of the individual layers of the aorta, where the inner layer of the aortic wall tears, or peels, away from the adjacent layer of the aorta. This separation of the layers creates an area, or a pathway, between the torn-away layer and the remainder of the aortic wall. The area created by the two layers is called a false lumen. As blood flows through the aorta, it travels through its normal pathway, referred to as the true lumen, but a portion of the blood also is directed into the false lumen.
The false lumen is a secondary flow path that does not provide any blood delivery to the remainder of the body. As blood continues to be diverted into the false lumen, the rate of blood flow and volume of diverted blood into the false lumen can result in the exertion of large forces against the aortic wall. These forces result in the further propagation of the tear, thereby creating a larger false lumen and greater associated forces. The propagation of the tear can eventually lead the aorta wall to rupture, which can result in death.
The type of treatment for this condition depends on the severity and location of the aortic tear. Medical therapy, such as blood pressure and cholesterol-lowering drugs, are typically provided as one method of treatment for this condition. Medical therapy is designed to limit further propagation of the tear and to reduce the chances of aortic rupture. This type of treatment is adequate when the condition is in its early stages and no significant tear exists. However, it is not designed to prevent the further propagation of a dissected portion of the aortic wall.
In situations where the condition has progressed to a point where the risk of aortic rupture or further propagation is higher, more aggressive types of treatment may be required. Such additional types of treatment include endovascular intervention and open surgical repair. Endovascular intervention is a minimally invasive procedure where a stent graft is placed within the damaged area. When expanded, the stent graft exerts a radial force along the damaged area, thereby forcing the dissected layer of the aorta against the adjacent layer of the aortic wall. In theory, retaining the dissected layer of the aorta against the adjacent layer of the aortic wall prevents blood from flowing into the dissected layer, thereby minimizing the blood flow into the false lumen. This type of treatment, however, only covers the dissected layer and sometimes does not fully occlude the false lumen formed between the dissected layer and the adjacent layer of the aortic wall. As a result, and typically in chronic aortic dissection cases, there is a likelihood that blood will continue to flow between the dissected layer and the adjacent aortic layer, thereby causing the dissected portion of the aortic wall to further separate from the adjacent layer of the aortic wall which allows additional blood to reenter the false lumen. Another disadvantage of this type of treatment is that it does not prevent the chances of future tears in the damaged area. As a result, endovascular repair is an inadequate method of treatment for patients suffering from chronic aortic dissection.
Open surgical repair is another type of treatment used to cure aortic dissection. This highly invasive procedure requires the replacement of the diseased portion of the aorta with a Dacron/ePTFE graft. The graft is sewn in the place of the removed portion of the aorta and on average requires a two-month recovery period. As true with other highly invasive medical procedures, open surgical repair is a lengthy procedure and subjects patients to a higher risk for stroke, ischemia, and other medical complications. As a result, this type of procedure is not recommended to treat aortic dissection cases unless no other treatment is available and carries a high likelihood of post-surgical complications.
Therefore, there is a need for another type of medical treatment to prevent against chronic aortic dissection while minimizing the complications related to open surgical treatment.